The present invention relates to cathodoluminescent flat display devices and specifically to a method for scanning such devices which employ a plurality of electron beam guides.
Recently, flat image display devices have been suggested having a viewing screen of about 75 .times. 100 cm. and a total depth of about 2.7 to 10.0 cm. One such device is described in U.S. patent application Ser. No. 607,492 entitled "Flat Electron Beam Addressed Device" filed on Aug. 25, 1975 by T. O. Stanley now U.S. Pat. No. 4,031,427. This type of device utilizes a plurality of electron beams which excite different portions of a large phosphor screen. A plurality of electron beam guides extends between the front and rear surfaces of the device to direct the electron beams to the proper area of the screen. In the original system, a separate electron beam guide was used for each picture element and each guide had a separate source for generating its own electron beam.
Conventional electron guns require excessive amounts of space and power to be practical in such systems. An alternate proposal has been to utilize a smaller number of electron guns and sequentially direct the beam from each gun into each of the beam guides during every line time so that, one at a time, each electron beam scans each electron beam guide. Although the latter system has considerable merit, in order to display a television image, the switching of the electron beams from one guide to another must occur at relatively high speed, e.g., 10 MHz. in order for each beam to go into each guide. The high switching speed necessitates rather complex and expensive control circuitry.